1. Field of the Invention
The present invention relates to a linear motion rolling guide unit, and more particularly, to a linear motion rolling guide unit equipped with a detection device that detects the relative position of a track rail and a slider.
2. Description of the Prior Art
An example of a linear motion rolling guide unit of the prior art is shown in FIG. 1. This linear motion rolling guide unit is disclosed in Japanese Laid-Open Patent Publication No. 3-153915.
As shown in FIG. 1, this linear motion rolling guide unit has track rail 1, in which tracks in the form of upper transfer surfaces 1a and lower transfer surfaces 1b are formed in the left and right shoulders along the lengthwise direction; slider 3 having four rolling element circulating paths 2 corresponding to each of these upper transfer surfaces 1a and lower transfer surfaces 1b, and which is able to move freely relative to track rail 1; and, a large number of rolling elements in the form of balls 5, which are arranged and contained within rolling element circulating paths 2, and bear the load between track rail 1 and slider 3 by circulating while rolling over the upper transfer surfaces 1a and lower transfer surfaces 1b accompanying the movement of the slider 3.
Attachment groove 1d is formed in the top of track rail 1 along its entire length, and a detected portion in the form of band-shaped scale 7 is arranged within this attachment groove 1d. This scale 7 is magnetized in a prescribed pattern along its lengthwise direction.
Magnetic head 8 is attached at a prescribed interval from and in opposition to scale 7 in slider 3. Magnetic head 8 emits a detection signal according to changes in the magnetic field. The relative positions of track rail 1 and slider 3 are detected based on detection signals from this magnetic head 8.
Scale 7 requires a somewhat large space to be provided on track rail 1 since it is of a band-shape and its surface area spreads, and selection of its installation site has little degree of freedom, thus creating a problem in terms of reducing the size of the linear motion rolling guide unit.